Hydrophobic fuel pack and well ignition therewith



United States Patent 3,323,591 HYDROPHOBIC FUEL PAQK AND WELL IGNITION THEREWITH Robert R. Harvey, Bartlesville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware No Drawing. Filed Oct. 19, 1964, Ser. No. 404,913 18 Claims. (Cl. 166-39) This invention relates to an improved method and fuel pack for in situ combustion ignition in a well borehole penetrating a carbonaceous stratum.

In recent years, the petroleum industry has been practicing in situ combustion in oil-bearing strata in the production of oil therefrom. One of the problems involved in this method of production is the ignition of the oil in the stratum to be produced around an ignition borehole penetrating the stratum. One of the most effective methods of ignition comprises packing the wellbore within the oilbearing stratum with a fuel pack such as charcoal, charcoal saturated with oil, porous refractory or ceramic aggregates saturated with heavy oil, mixtures of charcoal and other porous aggregates saturated with heavy oil, and various types of thermite. In some instances, the aggregates forming the fuel pack are dumped downhole from the well head to form a compact massof the aggregates at the bottom of the well. -In other instances the fuel aggregates are lowered in the borehole in a suitable bucket having a bottom drop-out, and sometimes the fuel pack is consolidated into a unitary mass above ground in cylindrical porous form with attaching means on its upper end for lowering into the well thru the casing. Another method comprises placing the porous fuel aggregates in an elongated permeable sheath, such as a net, and lowering the sheath containing the fuel aggregates into the well on a suitable cable or line.

US. Patents 3,010,513, issued to R. V. Gerner; 3,031,- 014, issued to H. W. Parker; and 3,048,223, issued to C. J. Helmers, are illustrative of various types of fuel packs for igniting subterranean carbonaceous strata. Usually the particulate porous aggregates are saturated with a hydrocarbon oil, preferably, a heavy oil such as diesel oil or diesel oil containing asphalt, before or after placing the aggregates in the well.

It has been discovered in field operation that a fuel pack which has been found to be highly efficient in igniting a carbonaceous stratum in one oil field has failed in another due to inability of the operator to ignite the fuel pack and burn the same in the borehole. It has also been discovered that the cause of the failure is the invasion of water into the fuel pack, particularly, when the fuel pack has been left in the well over night before attempting to start the same by igniting a starter material such as a fuse, thermite, or other igniter having its own oxygen supply. Another method of starting the fuel pack is to inject a combustible fuel gas-air mixture into the well either directly or thru the carbonaceous stratum from another well and ignite the gas within or on the fuel pack while providing more than the stoichiometric ratio of O to fuel gas and finally eliminating the fuel gas from the combustion-supporting gas entirely. Even though the wellbore is dried out before positioning the fuel pack, by passing dry hot air thru the borehole into the stratum or from the stratum, water may invade the wellbore and the fuel pack before the igniter is activated and prevent proper ignition of the fuel pack. On occasion, it has been necessary to dry the starter material and fuel pack by blowing dry air thru the borehole before ignition and in some instances it has been necessary to repack the well with completely fresh fuel material in order to effect ignition.

This invention is concerned with a novel and improved fuel pack and a method for overcoming the foregoing water-invasion problem.

Accordingly, it is an object of the invention to provide an improved fuel pack and method for igniting a subterranean carbonaceous stratum to initiate in situ combustion therein. Another object is to provide a non-wettable fuel pack and a method of preventing the invasion of water into a fuel pack in a borehole penetrating a carbonaceous stratum. A further object is to provide an improved method of igniting a carbonaceous stratum. Other objects of the invention will become apparent to one skilled in the art upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises a fuel pack consisting essentially of particulate porous solid fuel containing material impregnated with a minor but effective amount or concentration of an oil-soluble surfactant which renders the fuel pack oil-wettable and hydrophobic. Another aspect of the invention comprises impregnating a mass of porous, fuel-containing aggregates with an oilsoluble surfactant in minor but effective concentration to render the aggregates oil-wettable and hydrophobic, and positioning the oil-Wettable, hydrophobic mass in a well within a carbonaceous stratum which may contain water. The oil-soluble surfactant may be applied directly to the fuel aggregates as such or dissolved in a suitable oil which may also function as fuel in the pack.

The concentration of the surfactant in the fuel aggregates will vary with different types of fuel aggregates but will generally be in the range of 0.3 to 5 weight percent based on the weight of the aggregates and, preferably, in the range of 1 to 3 weight percent. When the surfactant is incorporated in an oil prior to impregnation or saturation of the porous aggregates, the amount of surfactant will generally be in the range of 0.2 to 5 weight percent based on the weight of the oil and, preferably, in the range of 1 to 3 weight percent.

Charcoal in the form of small pieces or briquets functions effectively without the incorporation of oil therein but functions more effectively when impregnated or saturated with a hydrocarbon oil, preferably, a heavy oil such as diesel oil or diesel oil containing a substantial proportion of asphalt. A 50/50 mixture of diesel oil and asphalt has been used in combination with charcoal to efficiently ignite a dry porous carbonaceous stratum. The surfactant may be applied to the dry charcoal directly or dissolved in a suitable oil solvent which does not necessarily saturate the charcoal but applies a coat of the surfactant substantially completely thereon. When utilizing porous refractory aggregates, the heavy oil is essential to the fuel pack since this is the sole source of fuel unless the aggregates are mixed with charcoal aggregates. In such an application, it is preferred to saturate both the charcoal and the ceramic aggregates with heavy oil.

Porous ceramic or refractory aggregates include alumina, silica, silica-alumina, mullite, etc. Porous crushed fire brick of various types provide excellent aggregates when soaked with diesel oil or a mixture of diesel oil and asphalt.

A wide variety of oil-wettable surfactants are available for use in the invention. Higher amines of 10-20 carbon atoms and salts thereof, such as octadecyl amine and dodecyl amine hydrochloride, fatty acid esters such as glyceryl stearate, and glyceryl oleate, mahogany sulfonates such as sulfonated oil fractions or sulfonated cycle oil, silicones and silicone oils illustrate the wide variety of oil soluble surfactants which render the fuel aggregates oil-wettable and hydrophobic. I

Other available surfactants which render solids oilwettable and hydrophobic are disclosed in US. Patents 3,098,038, issued to Thompson et al., July 16, 1963, and 3,032,499, issued to Brown, May 1, 1962. The invention is not limited to any particular surfactant or group of 3 surfactants but includes within its scope any oil-soluble surface active agent which renders fuel aggregates oilwettable and hydrophobic.

Specifically, a primary secondary, or tertiary amine, or quaternary ammonium salt which is oil soluble and renders the fuel aggregates oil-wettable and hydrophobic are particularly useful and desirable. Charcoal briquets were saturated with diesel fuel containing octadecyl amine in an amount in the range of 1 to weight percent based on the weight of the oil and were found to effectively prevent water intrusion into the mixture when sub merged in water and, surprisingly, this surfactant material increased the amount of oil accepted by the charcoal more than 100 percent. In other words, more than twice as much of the diesel oil by weight containing the octadecyl amine was imbibed by the charcoal when immersed therein than was imbibed under similar circumstances without the incorporation of the amine in the oil. Thus, the use of the surfactant not only increases the fuel-oil concentration in the fuel aggregates but also renders the fuel aggregates hydrophobic so as to protect the fuel pack from water invasion.

Certain modifications of the invention Will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

1. A f-uel pack of porous aggregates containing comhustible material, 0.3 to 5 weight percent (based on the weight of said aggregates) of an oil-soluble surfactant which renders the pack hydrophobic, and a saturating amount of a heavy oil, said pack being enclosed within an elongated cylindrical permeable sheath adapted to be lowered upright into a well.

2. The pack of claim 1 wherein said aggregates are principally charcoal.

3. The pack of claim 1 wherein said aggregates are principally charcoal and said surfactant comprises an amine of to carbon atoms.

4. The pack of claim 1 wherein said aggregates are principally charcoal and said surfactant comprises octadecyl amine.

5. The pack of claim 1 wherein said aggregates are principally charcoal and said surfactant comprises a fatty acid ester.

6. The pack of claim 1 wherein said aggregates are principally c-harcoal and said surfactant comprises a salt of an amine of 10 to 20 carbon atoms.

7. The pack of claim 1 wherein said aggregates are principally charcoal and said surfactant comprises a silicone oil.

8. The pack of claim 1 wherein said aggregates are principally charcoal and said surfactant comprises a mahogany sulfonate.

9. The method of preparing the fuel pack of claim 1 comprising incorporating said surfactant in a heavy oil in a concentration in the range of about 0.2 to 5 weight percent of the oil and saturating said aggregates with the resulting oil.

10. The process of claim 9 wherein said aggregates are impregnated with said surfactant followed by saturating same with a heavy oil.

11. A process comprising positioning the fuel pack of claim 1 in upright position in a well within a carbonaceous stratum containing water and igniting and burning said pack with an O -containing gas to ignite said stratum.

12. The process of claim 11 wherein said porous aggregates are principally charcoal.

13. The process of claim 11. wherein said surfactant is an amine of 10 to 20 carbon atoms and said porous aggregates are principally charcoal.

1.4. The process of claim 11 where said surfactant is octadecyl amine and said porous aggregates are principally charcoal.

15. The process of claim 11 wherein said surfactant is a fatty acid ester and said porous aggregates are principally charcoal.

1.6. The process of claim 11 wherein said surfactant is a salt of an amine of 10 to 20 carbon atoms and said porous aggregates are principally charcoal.

17. The process of claim 11 wherein said surfactant is a silicone oil and said porous aggregates are principally charcoal.

18. The process of claim 11 wherein said surfactant is a mahogany snlfonate and said porous aggregates are principally charcoal.

References Cited UNITED STATES PATENTS 2,078,755 4/1937 Frolich 44-6 2,448,605 9/1948 Kleinicke 44-6 X 2,621,115 12/1952 Van Order 44-6 2,670,047 2/1954 Mayes et al. 166-11 3,048,224 8/1962 Parker 166-39 X 3,055,427 9/1962 Pryor et al. 166-39 3,106,246 10/1963 Prentiss 166-39 X 3,126,952 3/1964 Jones 166-9 3,246,694 4/1966 Taber et al 166-9 OTHER REFERENCES The condensed Chemical Dictionary, sixth edition, Reinhold Publishing Co., New York, 1961 (pp. 40 and 438 relied on). (Copy in Group 354.)

CHARLES E. OCONNELL, Primary Examiner.

STEPHEN I. NOVOSAD, Examiner. 

1. A FUEL PACK OF POROUS AGGREGATES CONTAINING COMBUSTIBLE MATERIAL, 0.3 TO 5 WEIGHT PERCENT (BASE ON THE WEIGHT OF SAID AGGREGATES) OF AN OIL-SOLUBLE SURFACTANT WHICH RENDERS AND PAKC HYDROPHOBIC, AND A SATURATING AMOUNT OF A HEAVY OIL, SAID PACK BEING ENCLOSED WITHIN AN ELONGATGED CYLINDRICAL PERMEABLE SHEATH ADAPTED TO BE LOWERED UPRIGHT INTO A WELL.
 11. A PROCESS COMPRISING POSITIONING TEH FUEL PACK OF CLAIM 1 IN UPRIGHT POSITION IN A WELL WITHIN A CARBONACEOUS STRATUM CONTAINING WATER AND IGNITING AND BURNING SAID PACK WITH AN O2-CONTAINING GAS TO IGNITE SAID STRATUM. 